The present invention relates to interfaces, and more particularly to interfaces for transmission of data and other signals between two devices.
Various devices have been employed to interface electronic devices. One such device is the Aydin UXW-324 Interface, described in Aydin UXW-324 I/O: Interdata Mux Switch A25215TVD-193 Interface No. 150-6400-008. While such devices have served the purpose for some applications, they have not proven entirely satisfactory under all conditions of service for the following reasons. Where two different devices are being interfaced, having different speeds of operation, and it is decided to transmit information or other signals therebetween, the different speeds can cause loss of such information or other signal. Also, two different devices being interfaced can have different interrupt handling sequences, so that provision of an interrupt from a peripheral device to a computer having different interrupt handling sequences can result in sloppy interrupt handling, loss of interrupts, and system down time resulting from an interrupt being generated but not received. Also, it is necessary to provide some means of having one device inform the other when interrupt handling errors and other errors occur; otherwise, one device can go down or become inoperative because of an error without so informing the other device, which may continue to provide data or other signals thereto. Also, if several devices are together interfaced to another device on the same interface, errors can occur if the latter device is not informed as to which of the several devices it is communicating with, particularly if one of these several devices is generating an interrupt therefor. Also, it is necessary to inform the device receiving signals what sort of signals these are, and to insure that that device is ready to receive same. If one device has a smaller number of I/O lines than the other device, then it is necessary to utilize only the available lines. If more than one type of signal (such as status information or data information) is being applied to the same line, the receiving device would ordinarily be unable to determine the nature of the information being received. This can result in confusion in the system such as where a device is providing status information off an interrupt rather than status information from a data transfer so that it would appear that the transmitting device was processing data when it was generating an interrupt. Without servicing of the interrupt, the transmitting device would not return to its normal mode of operation, and confusion in the system and downtime would result without the system being able to correct such problems itself. This is especially true where one device cannot control when the other device could generate an interrupt.